1. Field of the Invention
This invention relates to an improved full-function brake valve for use in fluid pressure braking systems primarily employed on the semi-trailers of heavy-duty highway tractor-trailer vehicle combinations. More specifically, it relates to a simplified full-function brake valve which combines the functions of, and replaces, multiple separate brake valves on highway semi-trailers with concomitant advantages, and is also less complex and costly than other full-function valves designed for such purposes.
2. Discussion of Prior Art
To meet all of the emergency and service requirements of modern heavy-duty highway tractor-trailer combinations, while meeting all of the pertinent governmental regulations, including Federal Regulation FMVSS 121 (Docket 90-3, Notice 2), the trucking industry has resorted to a number of semi-trailer brake valve arrangements which have led to complexity, high costs, installation and maintenance difficulties and related problems. These valve arrangements include multiple valves with multiple complex inter-connections, all designed to carry out multiple requisite brake functions.
Manifestly, the various valve installations and interconnections to accomplish all of these functions on a modern tandem semi-trailer are complex, costly, difficult and inconvenient to install, troubleshoot, service and maintain and otherwise are undesirable from a parts inventory standpoint. Previous efforts to integrate the various valve requirements within a single envelope or housing have not resulted in brake systems meeting current requirements.
Illustrative of the prior art is Gross et al. U.S. Pat. No. 4,915,456 and patents cited therein, i.e., Ury U.S. Pat. Nos. 4,042,281, 4,080,004 and 4,163,585; Fannin U.S. Pat. No. 4,182,535; and Carton et al. U.S. Pat. Re. 30,205 (Reissue of U.S. Pat. No. 3,992,064). Still other illustrative prior art includes Fannin U.S. Pat. No. 4,472,001 and Campanini U.S. Pat. No. 4,593,954 and the patents cited therein. None of these patents disclose or suggest a simplified full-function valve, all housed within a single envelope and meeting regulatory requirements, such as provided by the present invention.
Current efforts to cope with the shortcomings of such prior art are reflected, for example, in Moody et al. U.S. Pat. No. 5,236,250 and Wallestad U.S. Pat. No. 5,322,353, both owned by the same assignee as herein. While successfully coping with and solving certain of the problems of the prior-art approaches, such current approaches have themselves introduced considerable complexity in the integrated valve assembly itself and some limitations performancewise, e.g., slower drive-away capability. Moreover, in the event of future changes in the regulatory or markets requirements for the performance of such full-function valves in certain respects, current designs will necessitate very-costly redesigns.